Electric pump

ABSTRACT

An electric pump may comprise a rotating body comprising a rotor and an impeller disposed juxtaposed to the rotor in a rotary shaft direction of the rotor, a stator disposed on an outer circumferential side of the rotor, a easing comprising a fluid passage formed along an outer circumference of the impeller, and configured to store the rotating body and the stator and a loading unit configured to constantly apply force on the rotating body during when the electric pump is operating, wherein the force being for reducing displacement of the rotating body caused by a pressure difference in the fluid passage generated when the electric pump is operating between a low pressure side where a pressure of fluid is low and a high pressure side where the pressure of the fluid is high within the fluid passage.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2012-117360 filed on May 23, 2012, the contents of which are hereby incorporated by reference into the present application.

TECHNICAL FIELD

The technique disclosed in the present application relates to an electric pump, and in particular, relates to an electric pump in which a rotor and an impeller are juxtaposed in a rotary shaft direction of the rotor.

DESCRIPTION OF RELATED ART

Japanese Patent Application Publication No. 2004-176552 discloses a DC pump in which a bladed wheel integrated with a magnet rotor is disposed outside a stator. The bladed wheel is disposed outside the outer circumference of the magnet rotor. The DC pump sucks fluid into the casing of the DC pump according to rotation of the bladed wheel, pressurizes the fluid, and then discharges the fluid outside the casing. The DC pump further comprises magnetic bodies disposed inside and outside the magnet rotor. The magnetic body applies magnetic force that balances the force applied to the bladed wheel resulting from a pressure difference of the fluid in the casing to the bladed wheel. As a result, the bladed wheel is suppressed from making contact with the casing.

SUMMARY

Japanese Patent Application Publication No. 2004-176552 does not take into consideration of an electric pump having a configuration in which a rotor and an impeller (the bladed wheel in the publication) are juxtaposed in a rotary shaft direction of the rotor. The present application provides an electric pump in which a rotor and an impeller are juxtaposed in a rotary shaft direction of the rotor, and displacement of the rotor and the impeller resulting from a pressure difference of the fluid in the casing is suppressed.

Disclosed herein is an electric pump that may comprise a rotating body, a stator, a casing, and a loading unit. The rotating body may comprise a rotor and an impeller disposed juxtaposed to the rotor in a rotary shaft direction of the rotor. The stator may be disposed on an outer circumferential side of the rotor. The casing may comprise a fluid passage formed along an outer circumference of the impeller. The casing may be configured to store the rotating body and the stator. The loading unit may be configured to constantly apply force on the rotating body during when the electric pump is operating. The force may be for reducing displacement of the rotating body caused by a pressure difference in the fluid passage generated when the electric pump is operating between a low pressure side where a pressure of fluid is low and a high pressure side where the pressure of the fluid is high within the fluid passage.

In the electric pump, when the impeller rotates, fluid is sucked into the casing and flows through a fluid passage. The fluid in the fluid passage is pressurized with rotation of the impeller and is discharged outside the fluid passage. The fluid is pressurized when the fluid flows in the fluid passage. Thus, the fluid pressure on the downstream side of the fluid passage is higher than the fluid pressure on the upstream side. As a result, during the operation of the electric pump, a pressure difference of the fluid occurs in the fluid passage. The fluid pressure difference causes the fluid to apply force to the rotating body so that the rotating body is displaced.

In the electric pump, during the operation of the electric pump, the loading unit constantly applies force for suppressing displacement of the rotating body resulting from the fluid pressure difference to the rotating body. According to this configuration, displacement of the rotating body resulting from a fluid pressure difference in the fluid passage is suppressed. As a result, contacting between the rotating body and the casing is suppressed, and a decrease in pumping efficiency resulting from the contacting between the rotating body and the casing is suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic longitudinal cross-sectional view of an electric pump according to a first embodiment.

FIG. 2 shows a cross-sectional view taken along line II-II of FIG. 1.

FIG. 3 shows a stator as seen from the top of FIG. 1.

FIG. 4 shows a longitudinal cross-sectional view of a stator according to a second embodiment.

FIG. 5 shows a view for explaining a core according to a third embodiment.

FIG. 6 shows a view for explaining a core according to a fourth embodiment.

FIG. 7 shows a view for explaining a core according to a fifth embodiment.

FIG. 8 shows a cross-sectional view taken along line VIII-VIII of FIG. 7.

FIG. 9 shows a schematic longitudinal cross-sectional view of an electric pump according to a sixth embodiment.

FIG. 10 shows a schematic longitudinal cross-sectional view of an electric pump according to a seventh embodiment.

FIG. 11 shows a schematic longitudinal cross-sectional view of an electric pump according to an eighth embodiment.

FIG. 12 shows a cross-sectional view of an electric pump according to a ninth embodiment, taken along line II-II of FIG. 1.

FIG. 13 shows a schematic longitudinal cross-sectional view of an electric pump according to a tenth embodiment.

FIG. 14 shows an enlarged view of a portion indicated by XIV of FIG. 1, showing a configuration of a permanent magnet according to an eleventh embodiment.

FIG. 15 shows a configuration of a core according to a modification.

DETAILED DESCRIPTION

First, the features of embodiments described below will be described. The features described herein each independently have technical usefulness.

(First Feature) A loading unit may comprise a first configuration, a second configuration, or both of the first and second configurations. The first configuration may be a configuration in which resultant force of magnetic force loaded on an end portion of a rotor on an impeller side is directed from the low pressure side to the high pressure side. The second configuration may be a configuration in which resultant force of magnetic force loaded on an end portion of the rotor on an opposite side from the impeller is directed from the high pressure side to the low pressure side.

During the operation of the electric pump, strong force resulting from a pressure difference in the fluid passage acts on the impeller within the rotating body. As a result, the fluid pressure difference causes force to be applied to the rotating body such that the rotating body rotates in a direction where the impeller moves from the high pressure side to the low pressure side in relation to the rotor. According to this configuration, due to any one or both of the first and second configuration, force for suppressing displacement (i.e., rotation) of the rotating body may be appropriately applied to the rotating body.

(Second Feature) The loading unit may include a stator and a rotor. The first configuration may include a configuration in which an area of the stator extending along the end portion of the rotor on the impeller side on the high pressure side is larger than an area of the stator extending along the end portion of the rotor on an impeller side on the low pressure side. The second configuration may include a configuration in which an area of the stator extending along the end portion of the rotor on the opposite side from the impeller on the low pressure side is larger than an area of the stator extending along the end portion of the rotor on the opposite side from the impeller on the high pressure side.

According to this configuration, the loading unit may realize the first and second configurations using the stator and the rotor. In the first configuration, the magnetic force directed to the high pressure side may be increased in the end portion of the rotor closer to the impeller. In the second configuration, the magnetic force directed to the low pressure side may be increased in the end portion of the tutor opposite to the impeller. As a result, the force for suppressing displacement of the rotating body may be appropriately applied to the rotating body. Further, it is not necessary to provide a configuration exclusively for generating the force for suppressing displacement of the rotating body.

(Third Feature) The first configuration may include a configuration in which an end portion of a high pressure-side stator portion positioned on the high pressure side of the stator extends toward the impeller side along the rotary shaft direction than an end portion of a low pressure-side stator portion positioned on the low pressure side of the stator. The second configuration may include a configuration in which an end portion of the low pressure-side stator portion on the opposite side from the impeller extends toward the opposite side from the impeller along the rotary shaft direction than an end portion of the high pressure-side stator portion on the opposite side from the impeller.

During the operation of the electric pump, a voltage is applied to the stator, whereby magnetic force directed to the stator is applied to the rotor. According to the first configuration, magnetic force directed from the low pressure side to the high pressure side to the rotating body may be applied in the end portion of the rotor closer to the impeller. Moreover, according to the second configuration, magnetic force directed from the high pressure side toward the low pressure side to the rotating body may be applied in the end portion of the rotor opposite to the impeller. Due to this, the force for suppressing displacement of the rotating body may be appropriately applied to the rotating body.

(Fourth Feature) The first configuration may include a configuration in which a length of a high pressure-side stator portion extending along an outer circumferential surface of the rotor is longer than a length of a low pressure-side stator portion extending along the outer circumferential surface of the rotor in a cross section vertically intersecting a rotary shaft at the end portion of the rotor on the impeller side. The second configuration may include a configuration in which a length of the low pressure-side stator portion extending along the outer circumferential surface of the rotor is longer than a length of the high pressure-side stator portion extending along the outer circumferential surface of the rotor in a cross section vertically intersecting the rotary shaft at the end portion of the rotor on the opposite side from the impeller.

(Fifth Feature) The load unit may include a stator and a rotor. The first configuration may include a configuration in which an average gap size between the rotor and a high pressure-side stator portion positioned on the high pressure side of the stator is smaller than an average gap size between the rotor and a low pressure-side stator portion positioned on the low pressure side of the stator at the end portion of the rotor on the impeller side. The second configuration may include a configuration in which an average gap size between the rotor and the low pressure-side stator portion is smaller than an average gap size between the rotor and the high pressure-side stator portion at the end portion of the rotor on the opposite side from the impeller.

In the fourth and fifth features, according to the first configuration, magnetic force directed from the low pressure side to the high pressure side to the rotating body may be applied in the end portion of the rotor closer to the impeller. Moreover, according to the second configuration, it is possible to apply magnetic force directed from the high pressure side toward the low pressure side to the rotating body in the end portion of the rotor opposite to the impeller. Due to this, the force for suppressing displacement of the rotating body can be appropriately applied to the rotating body.

(Sixth Feature) The loading unit may include a first magnetic body and a second magnetic body. The first magnetic body may be attached to the rotating body and circumscribing in a circumferential direction of the rotating body. The second magnetic body may be attached to a region of the casing that faces the first magnetic body. The second magnetic body may comprise a first magnetic sub-body, a second magnetic sub-body, or both the first and second magnetic sub-bodies. The first magnetic sub-body may be disposed on the high pressure side, and generate magnetic force in a direction that draws the first magnetic body toward the second magnetic body. The second magnetic sub-body may be disposed on the low pressure side, and generate magnetic force in a direction that presses the first magnetic body toward an opposite side from the second magnetic body.

According to this configuration, due to the magnetic force generated by the first and second magnetic bodies, the force for suppressing displacement of the rotating body may be appropriately applied to the rotating body.

(Seventh Feature) The first magnetic body may be attached to the impeller.

According to this configuration, the magnetic force generated by the first and second magnetic bodies may be directly applied to the impeller on which strong force resulting from the fluid pressure difference acts.

(Eighth Feature) The first magnetic body may be attached to an end surface of the rotor on the opposite side from the impeller.

According to this configuration, using a configuration other than the rotor and the stator, the force for suppressing displacement of the rotating body can be appropriately applied to the rotating body.

(Ninth Feature) The loading unit may include a circumferential wall that covers the stator and surrounds a circumference of the rotor. The fluid passage may communicate with a gap between the circumferential wall and the rotor. The loading unit may include a third configuration, a fourth configuration, or both the third and fourth configurations. The third configuration may be a configuration in which a gap between the circumferential wall and the rotor on the low pressure side is larger than a gap between the circumferential wall and the rotor on the high pressure side at the end portion of the rotor on the impeller side, and the fourth configuration may be a configuration in which a gap between the circumferential wall and the rotor on the high pressure side is larger than a gap between the circumferential wall and the rotor on the low pressure side at the end portion of the rotor on the opposite side from the impeller.

In this configuration, fluid flows into the gap between the rotor and the circumferential wall and flows through the gap between the rotor and the circumferential wall. When the fluid flows from a region where the gap between the rotor and the circumferential wall is relatively small to a region where the gap between the rotor and the circumferential wall is relatively large, the fluid pressure increases. According to the former configuration, due to the pressure of the fluid present in the gap between the rotor and the circumferential wall, force directed from the low pressure side and the high pressure side in the end portion of the rotor closer to the impeller is applied to the rotating body. Moreover, according to the latter configuration, due to the pressure of the fluid present in the gap between the rotor and the circumferential wall, force directed from the high pressure side to the low pressure side in the end portion of the rotor opposite to the impeller is applied to the rotating body. As a result, the force for suppressing displacement of the rotating body may be appropriately applied to the rotating body.

(Tenth Feature) The loading unit may include a facing wall that faces an end surface of the rotor on the opposite side from the impeller. The fluid passage may communicate with a gap between the facing wall and the rotor. The loading unit may include a configuration in which a gap between the facing wall and an end surface of the rotor on the opposite side from the impeller that is on the low pressure side is larger than a gap between the facing wall and an end surface of the rotor on the opposite side from the impeller that is on the high pressure side.

In this configuration, fluid flows into the gap between the rotor and the facing wall and flows through the gap between the rotor and the facing wall. When the fluid flows from a region where the gap between the rotor and the facing wall is relatively small to a region where the gap between the rotor and the facing wall is relatively large, the fluid pressure increases. According to the configuration, due to the pressure of the fluid present in the gap between the rotor and the facing wall, force for suppressing displacement of the rotating body may be properly applied to the rotating body.

Representative, non-limiting examples of the present invention will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved power pumps, as well as methods for using and manufacturing the same.

Moreover, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described and below-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

First Embodiment Configuration of Electric Pump 10

An electric pump 10 is provided in an engine room of an automobile and used for circulating a coolant that cools an engine, an inverter, and the like. As shown in FIG. 1, the electric pump 10 comprises a pump unit 20 and a motor unit 40. The outer circumference of the electric pump 10 forms a casing 12. The casing 12 comprises an upper casing 28 and a lower casing 46.

(Configuration of Pump Unit 20)

The pump unit 20 is provided in the upper casing 28. In the pump unit 20, an inlet port 22, a discharge port 23 (see FIG. 2), and a coolant passage 24 are formed by the upper casing 28. Moreover, the pump unit 20 comprises an impeller 26 of a rotating body 60 described later. The impeller 26 is stored in the upper casing 28. As shown in FIG. 2, the impeller 26 has a circular shape when seen from the top of FIG. 1. When power is supplied to the electric pump 10, the impeller 26 rotates in a rotation direction R. A plurality of blades is formed at constant intervals on the upper surface of the impeller 26. The coolant passage 24 is formed between an outer circumferential surface of the impeller 26 and an inner circumferential surface of the upper casing 28.

The coolant passage 24 is formed along the outer circumference (that is, the rotation direction R) of the impeller 26. The inner circumferential surface of the upper casing 28 when seen in a cross-section parallel to the XY plane is gradually separated from the outer circumference of the impeller 26 as it advances in the rotation direction R. Thus, the passage area of the coolant passage 24 gradually increases along the rotation direction R. The coolant passage 24 is connected to the discharge port 23 at a position where the passage area of the coolant passage 24 is the largest. The discharge port 23 extends in a tangential direction of the coolant passage 24. The coolant passage 24 surrounds in a circumferential direction of the impeller 26. A portion of the coolant passage 24 where the passage area is the largest is connected to a portion of the coolant passage 24 where the passage area is the smallest.

As shown in FIG. 1, the inlet port 22 is further connected to the coolant passage 24. The inlet port 22 is formed in an upper end of the pump unit 20. The inlet port 22 extends in the extension direction of a rotary shaft of the rotating body 60 (this will be referred to simply as a “rotary shaft”).

(Configuration of Motor Unit 40)

The motor unit 40 is disposed under the pump unit 20. The motor unit 40 is formed in the lower casing 46. The motor unit 40 forms a brushless motor. The motor unit 40 comprises a shaft 16, a rotor 42 of the rotating body 60, and a stator 44. The lower end of the shaft 16 is fixed to the lower casing 46. The shaft 16 extends vertically within the casing 12, and a tip end thereof reaches the pump unit 20. The rotating body 60 is rotatably attached to the shaft 16. The rotating body 60 comprises the impeller 26 and the rotor 42. The rotor 42 is disposed under the impeller 26 with a gap interposed. The rotor 42 and the impeller 26 are juxtaposed in a rotary shaft direction of the rotating body 60 (that is, a rotary shaft direction of the rotor 42) (hereinafter referred to as a “Z-axis direction”). The rotor 42 and the impeller 26 rotate about the center of the shaft 16. The rotor 42 is stored in the lower casing 46. The rotor 42 has a cylindrical shape. The rotor 42 comprises a plurality of permanent magnets 52. The plurality of permanent magnets 52 is disposed in the circumferential direction so as to have a plurality of magnetic poles. The impeller 26 and the rotor 42 are integrated. Thus, when the rotor 42 rotates, the impeller 26 also rotates.

A control circuit 18 that controls the supply of power to the stator 44 is disposed under the motor unit 40. The control circuit 18 is connected to an external power supply (for example, a battery mounted on the vehicle) (not shown) by a terminal 14. The control circuit 18 supplies power supplied from the external power supply to the motor unit 40.

(Configuration of Stator 44)

The stator 44 is disposed on the outer circumferential side of the rotor 42. FIG. 1 shows a longitudinal cross-section of the stator 44, in which parallel diagonal lines are not depicted so that the figure can be easily understood. The stator 44 is stored in the lower casing 46. The stator 44 comprises two cores 44 a and 44 b. The two cores 44 a and 44 b are covered by a resin layer that forms the lower casing 46. The lower casing 46 comprises a circumferential wall 46 a that faces an outer circumferential surface 42 a of the rotor 42 and surrounds the outer circumference of the rotor 42 and a facing wall 46 b that faces an end surface 42 b of the rotor 42 opposite to the impeller 26. The rotor 42 is disposed between the circumferential wall 46 a and the facing wall 46 b with a gap interposed. The gap between the rotor 42 and the circumferential wall 46 a and the gap between the rotor 42 and the facing wall 46 b communicate with the pump unit 20 (that is, the coolant passage 24).

The two cores 44 a and 44 b are respectively formed by stacking a plurality of core plates 48 in the Z-axis direction. In this case, a larger number of core plates 48 are included in the core 44 b positioned on a side (that is, the left side of FIG. 1) where the passage area of the coolant passage 24 is relatively large than the core plates 48 included in the core 44 a positioned on a side (that is, the right side of FIG. 1) where the passage area of the coolant passage 24 is relatively small. That is, the length of the care 44 b in the Z-axis direction is larger than the length of the core 44 a in the Z-axis direction. Specifically, in the Z-axis direction, the position of an end of the core 44 b opposite to the pump unit 20 (that is, the impeller 26) is identical to the position of an end of the core 44 a opposite to the impeller 26, whereas the position of an end of the core 44 b closer to the impeller 26 is closer to the impeller 26 than an end portion of the core 44 a closer to the impeller 26. In other words, the end portion of the core 44 b closer to the impeller 26 extends closer toward the impeller 26 along the Z-axis direction than the end poartion of the core 44 a closer to the impeller 26. Moreover, in the Z-axis direction, the end of the core 44 b closer to the impeller 26 is positioned approximately at the same position as the end of the rotor 42 closer to the impeller 26.

As shown in FIG. 3, the core 44 a comprises three teeth 70 juxtaposed in the Y-direction. A coil 50 is wound around each tooth 70 with a bobbin made from a resin interposed. The core 44 b has the same configuration as the core 44 a except for the number of core plates 48 included therein.

(Operation of Electric Pump 10)

Next, the operation of the electric pump 10 will be described. When power is supplied from the external power supply to the electric pump 10 through the terminal 14, the control circuit 18 applies a voltage to the coils 50 wound around the six teeth 70 according to a predetermined order. As a result, a voltage of the same phase (that is, any one of U, V, and W phases) is applied to two teeth of the six teeth 70 that face each other with the shaft 16 interposed. That is, the motor unit 40 is a 3-phase AC motor.

When a voltage is applied to the coil 50, the teeth 70 on which the coils 50 are wound are magnetized. When the teeth 70 are magnetized, the permanent magnet 52 of the rotor 42 is pulled to the magnetized teeth 70. As a result, the rotating body 60 rotates about the shaft 16. With rotation of the impeller 26, the coolant is sucked into the pump unit 20 through the inlet post 22 and flows into the coolant passage 24. As shown in FIG. 2, the coolant in the coolant passage 24 flows in the rotation direction R through the coolant passage 24 while being pressurized with the rotation of the impeller 26 and is discharged outside the coolant passage 24 through the discharge port 23. The expression “during the operation of the electric pump 10” means the period when power is supplied to the coil 50 and the coolant is discharged outside the coolant passage 24 with the rotation of the rotating body 60. The expression “during the operation of the electric pump 10” does not mean the entire period when power is supplied to the coil 50.

As a result, during the operation of the electric pump 10, the pressure of the coolant in the coolant passage 24 on the downstream side is higher than the pressure of the coolant on the upstream side, and a pressure difference occurs in the coolant. Specifically, as shown in FIG. 2, the pressure of the coolant increases along the rotation direction R of the coolant passage 24, and the pressure of the coolant on the high pressure region HP is very higher than the pressure of the coolant on the low pressure region LP. Due to the pressure difference between the coolant pressure on the high pressure region HP and the coolant pressure on the low pressure region LP, force (hereinafter referred to simply as “force of pressure difference”) directed from the high pressure region HP and the low pressure region LP is applied to the impeller 26.

The force of pressure difference is applied to the vicinity of the upper end in FIG. 1, of the rotating body 60. That is, rotational force is applied to the rotating body 60 in such a direction (that is, the clockwise direction in FIG. 1) that the rotating body 60 rotates about an axial line that passes through the intermediate position in the Z-axis direction of the rotating body 60 so that the impeller 26 moves from the high pressure region HP to the low pressure region LP in relation to the rotor 42.

As shown in FIG. 1, in the electric pump 10, the core 44 b positioned on a side where the passage area of the coolant passage 24 is relatively large (that is, the side closer to the high pressure region HP) extends closer to the impeller 26 than the core 44 a positioned on a side where the passage area of the coolant passage 24 is relatively small (that is, the side closer to the low pressure region LP). Thus, when the teeth 70 are magnetized during the operation of the electric pump 10, the magnetic force directed toward the high pressure region HP is stronger than the magnetic force directed toward the low pressure region LP in the end portion of the rotor 42 closer to the impeller 26. As a result, the resultant force of the magnetic force applied to the end portion of the rotor 42 closer to the impeller 26 is directed from the low pressure region LP to the high pressure region HP. According to this configuration, force for suppressing the displacement (that is, rotation resulting from a coolant pressure difference) of the rotating body 60 can be appropriately applied to the rotating body 60. Moreover, since a voltage is supplied to the coil 50 during the operation of the electric pump 10, the resultant force of the magnetic force is constantly applied to the rotating body 60 during the operation of the electric pump 10. According to this configuration, it is possible to suppress the displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. As a result, the contacting between the rotating body 60 and the casing 12 is suppressed, and a decrease in the pumping efficiency of the electric pump 10 is suppressed. Since the resultant force of the magnetic force is constantly applied to the rotating body 60 during the operation of the electric pump 10, it is possible to suppress the force applied to the rotating body 60 from changing during the operation of the electric pump 10 and to suppress the posture of the rotating body 60 from becoming instable.

The resultant force of the magnetic force is generated by the stator 44 and the rotor 42. According to this configuration, it is not necessary to provide a configuration exclusively for generating the force for suppressing displacement of the rotating body 60. The rotor 42 and the stator 44 are an example of a “loading unit”.

Second Embodiment

Differences from the first embodiment will be described with reference to FIG. 4. FIG. 4 shows only the external shape of the rotating body 60 and actually has the same configuration as the first embodiment. A stator 144 comprises two cores 144 a and 144 b. The two cores 144 a and 144 b have the same configuration and are positioned at different positions in the Z-axis direction. Specifically, the core 144 b positioned on the high pressure region HP (the left side of FIG. 4) is positioned closer to the impeller 26 than the core 144 a positioned on the low pressure region LP (the right side of FIG. 4). In other words, the core 144 b positioned on the high pressure region HP extends closer to the impeller 26 in the Z-axis direction than the core 144 a positioned on the low pressure region LP, and the core 144 a positioned on the low pressure region LP extends closer to the side opposite to the impeller 26 in the Z-axis direction than the core 144 b positioned on the high pressure region HP.

According to this configuration, the same advantages as the first embodiment can be obtained. Further, the core 144 a positioned on the low pressure region LP extends closer to the side opposite to the impeller 26 than the core 144 b positioned on the high pressure region HP. Thus, when the teeth of the cores 144 a and 144 b are magnetized during the operation of the electric pump 10, the magnetic force directed toward the low pressure region LP is stronger than the magnetic force directed toward the high pressure region HP in the end portion of the rotor 42 opposite to the impeller 26. As a result, the resultant force of the magnetic force applied to the end portion of the rotor 42 opposite to the impeller 26 is directed from the high pressure region HP to the low pressure region LP. According to this configuration, the force for suppressing the displacement (that is, the rotation resulting from the coolant pressure difference) of the rotating body 60, that is, the force for suppressing the momentum of the rotating body 60 resulting from the force of pressure difference can be appropriately applied to the rotating body 60. According to this configuration, it is possible to further suppress the displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. The rotor 42 and the stator 144 are an example of a “loading unit”.

In a modification, the end portions of the cores 144 a and 144 b closer to the impeller 26 may be at the same position in the Z-axis direction. On the other hand, the end portion of the core 144 a opposite to the impeller 26 may extend closer to the side opposite to the impeller 26 in the Z-axis direction than the end portion of the core 144 b opposite to the impeller 26. According to this configuration, since the resultant force of the magnetic force applied to the end portion of the rotor 42 opposite to the impeller 26 is directed from the high pressure region HP to the low presure region LP, force can be appropriately applied to the rotating body 60.

Third Embodiment

As shown in FIG. 5, an electric pump 10 of the present embodiment is different from the electric pump 10 of the first embodiment, in that two cores 244 a and 244 b have a configuration different from that of the two cores 44 a and 44 b. The other configuration is the same as the electric pump 10 of the first embodiment, and description thereof will not be provided. The two cores 244 a and 244 b we respectively formed by stacking a plurality of core plates 248 in the Z-axis direction. The two cores 244 a and 244 b have the same number of core plates 248. That is, the lengths of the two cores 244 a and 244 b in the Z-axis direction are the same.

The plurality of core plates 248 comprises a first core plate 248 a and a second core plate 248 b. A portion of the first care plate 248 a extending along the outer circumferential surface 42 a of the rotor 42 among the portions that constitute the three teeth 270 a to 270 c is shorter than that of the second care plate 248 b.

In the core 244 a on the low pressure region LP (that is, the right side of FIG. 5), a partial core plate 248 (for example, a core plate 248 corresponding to ¼ of the length of the core plate 248 in the Z-axis direction) positioned at the end portion closer to the impeller 26 among the plurality of core plates 248 is the first core plate 248 a, and the other core plate is the second core plate 2486 b. On the other hand, in the core 244 b on the high pressure region HP (that is, on the left side in FIG. 5), a partial core plate 248 (for example, a core plate 248 corresponding to ¼ of the length of the core plate 248 in the Z-axis direction) positioned on the side opposite to the impeller 26 among the plurality of core plates 248 is the first core plate 248 a, and the other core plate is the second core plate 248 b.

In this configuration, the length of the core 244 b (a portion formed of the second core plate 248 b) extending along the outer circumferential surface 42 a is larger than the length of the core 244 a (a portion formed of the first core plate 248 a) extending along the outer circumferential surface 42 a when seen in a cross-section (that is, a cross-section orthogonal to the Z-axis direction) parallel to the XY-plane, of the end portion of the rotor 42 closer to the impeller 26. When the teeth of the cores 244 a and 244 b are magnetized during the operation of the electric pump 10, in the end portion of the rotor 42 closer to the impeller 26, the magnetic force directed toward the core 244 b (that is, toward the high pressure region HP) between the core 244 b and the rotor 42 is stronger than the magnetic force directed toward the core 244 a (that is, toward the low pressure region LP) between the core 244 a and the rotor 42. That is, the resultant force of the magnetic force applied to the end portion of the rotor 42 closer to the impeller 26 is directed from the low pressure region LP toward the high pressure region HP. According to this configuration, force for suppressing the displacement (that is, rotation resulting from a coolant pressure difference) of the rotating body 60 can be appropriately applied to the rotating body 60. Moreover, since a voltage is supplied to the coil 50 during the operation of the electric pump 10, the resultant force of the magnetic force is constantly applied to the rotating body 60 during the operation of the electric pump 10. According to this configuration, it is possible to suppress the displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. As a result, the contacting between the rotating body 60 and the casing 12 is suppressed, and a decrease in the pumping efficiency of the electric pump 10 is suppressed.

The length of the core 244 a extending along the outer circumferential surface 42 a (that is, a portion formed of the second core plate 248 b) is larger than the length of the core 244 b extending along the outer circumferential surface 42 a (that is, a portion formed of the first care plate 248 a) when seen in a cross-section parallel to the XY-plane, of the end portion of the rotor 42 opposite to the impeller 26. In this configuration, during the operation of the electric pump 10, in the end portion of the rotor 42 opposite to the impeller 26, the magnetic force directed toward the core 244 a between the core 244 a and the rotor 42 (that is, toward the low pressure region LP) is stronger than the magnetic force directed toward the core 244 b between the core 244 b and the rotor 42 (that is, toward the high pressure region HP). That is, the resultant force of the magnetic force applied to the end portion of the rotor 42 opposite to the impeller 26 is directed from the high pressure region HP toward the low pressure region LP. According to this configuration, the force for suppressing the displacement (that is, the rotation resulting from the coolant pressure difference) of the rotating body 60, that is, the force for suppressing the momentum of the rotating body 60 resulting from the force of pressure difference can be appropriately applied to the rotating body 60. According to this configuration, it is possible to further suppress the displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24.

In a modification, any one of the two cores 244 a and 244 b may include only the second core plate 248 b.

Fourth Embodiment

As shown in FIG. 6, an electric pump 10 of the present embodiment is different from the electric pump 10 of the third embodiment, in that a first core plate 348 a formed in two cores 344 a and 344 b has a different shape from that of the first core plate 248 a. A second core plate 348 b has the same shape as the second care plate 248 b.

Portions of the second core plate 348 b constituting three teeth 370 a to 370 c have a portion that extends along the outer circumference of the rotor 42. On the other hand, an end portion of the first core plate 348 a closer to the rotor 42 among the portions that constitute the three teeth 370 a to 370 c does not extend along the outer circumference of the rotor 42 and is further separated from the outer circumference of the rotor 42 than that of the second core plate 348 b.

In this configuration, the length of the core 344 b extending along the outer circumferential surface 42 a (that is, a portion formed of the second core plate 348 b) is larger than the length of the care 344 a extending along the outer circumferential surface 42 a (that is, a portion formed of the first core plate 348 a) when seen in a cross-section parallel to the XY-plane, of the end portion of the rotor 42 closer to the impeller 26. Moreover, the length of the core 344 a extending along the outer circumferential surface 42 a (that is, a portion formed of the second core plate 3486 b) is larger than the length of the core 344 b extending along the outer circumferential surface 42 a (that is, a portion formed of the first core plate 348 a) when seen in a cross-section parallel to the XY-plane, of the end portion of the rotor 42 opposite to the impeller 26. According to this configuration, the electric pump 10 of the fourth embodiment can provide the same advantages as the electric pump 10 of the third embodiment. In a modification, any one of the two cores 344 a and 344 b may comprise only the second core plate 348 b.

Fifth Embodiment

As shown in FIG. 7, an electric pump 10 of the present embodiment is different from the electric pump 10 of the third embodiment, in that a first core plate 448 a formed in two cores 444 a and 444 b has a different shape from that of the first core plate 248 a. A second core plate 448 b has the same shape as the second core plate 248 b.

Portions of each of the first and second core plates 448 a and 448 b constituting three teeth 470 a to 470 c have a portion that extends along the outer circumferential surface 42 a. The portion of the first core plate 448 a extending along the outer circumferential surface 42 a is further separated from the outer circumferential surface 42 a than the portion of the second core plate 448 b extending along the outer circumferential surface 42 a.

In this configuration, as shown in FIG. 8, in the end portion of the rotor 42 closer to the impeller 26, the gap between the core 444 b (that is, a portion formed of the second core plate 448 b) and the rotor 42 is smaller than the gap between the core 444 a (that is, a portion formed of the first core plate 448 a) and the rotor 42. In this configuration, when the teeth of the cores 444 a and 444 b are magnetized during the operation of the electric pump 10, the magnetic force directed toward the core 444 b (that is, toward the high pressure region HP) between the core 444 b and the rotor 42 in the end portion of the rotor 42 closer to the impeller 26 is stronger than the magnetic force directed toward the core 444 a (that is, toward the low pressure region LP) between the core 444 a and the rotor 42. That is, the resultant force of the magnetic force applied to the end portion of the rotor 42 closer to the impeller 26 is directed from the low pressure region LP to the high pressure region HP.

Moreover, in the end portion of the rotor 42 opposite to the impeller 26, the gap between the core 444 a (that is, a portion formed of the second core plate 448 b) and the rotor 42 is smaller than the gap between the core 444 b (that is, a portion formed of the first core plate 448 a) and the rotor 42. Thus, when the teeth of the cores 444 a and 444 b are magnetized during the operation of the electric pump 10, the magnetic force directed toward the core 444 a (that is, toward the low pressure region LP) between the core 444 a and the rotor 42 in the end portion of the rotor 42 opposite to the impeller 26 is stronger than the magnetic force directed toward the core 444 b (that is, toward the high pressure region HP) between the core 444 b and the rotor 42. That is, the resultant force of the magnetic force applied to the end portion of the rotor 42 opposite to the impeller 26 is directed from the high pressure region HP to the low pressure region LP. According to these configurations, the electric pump 10 of the fifth embodiment can provide the same advantage as the electric pump 10 of the third embodiment.

In the above embodiment, the gap between the first core plate 448 a and the rotor 42 is constant. However, the gap between the first core plate 448 a and the rotor 42 may not be constant. In this case, an average size of the gap between the first core plate 448 a and the rotor 42 may be set to be larger than an average size of the gap between the second core plate 448 b and the rotor 42. In another modification, any one of the two cores 444 a and 444 b may include only the second core plate.

Sixth Embodiment

Differences from the electric pump 10 of the first embodiment will be described with reference to FIG. 9. In an electric pump 10 of the present embodiment, two pressurizing concave portions 500 and 502 are formed on a circumferential wall 46 a. The pressurizing concave portion 500 extends in the Z-axis direction from an end portion of the circumferential wall 46 a closer to the impeller 26 and reaches an intermediate position of the rotor 42 while passing through the end portion of the rotor 42 closer to the impeller 26. The pressurizing concave portion 500 is formed in a partially circular pipe shape along the outer circumferential surface 42 b on the low pressure region LP. A portion of the circumferential wall 46 a where the pressurizing concave portion 500 is formed is further separated from the rotor 42 than the other portion of the circumferential wall 46 a. That is, in the end portion of the rotor 42 closer to the impeller 26, the gap between the rotor 42 and the circumferential wall 46 a on the low pressure region LP is larger than the gap between the rotor 42 and the circumferential wall 46 a on the high pressure region HP.

The pressurizing concave portion 502 extends in the Z-axis direction from an end portion of the circumferential wall 46 a opposite to the impeller 26 and reaches an intermediate position of the rotor 42 while passing through the end portion of the rotor 42 opposite to the impeller 26. The two pressurizing concave portions 500 and 502 partially overlap in the Z-axis direction. The pressurizing concave portion 502 is formed in a partially circular pipe shape along the outer circumference of the rotor 42 on the high pressure region HP. A portion of the circumferential wall 46 a where the pressurizing concave portion 502 is formed is further separated from the rotor 42 than the other portion of the circumferential wall 46 a. That is, in the end portion of the rotor 42 opposite to the impeller 26, the gap between the rotor 42 and the circumferential wall 46 a on the high pressure region HP is larger than the gap between the rotor 42 and the circumferential wall 46 a on the low pressure region LP.

During the operation of the electric pump 10, a portion of the coolant in the coolant passage 24 flows into the gap between the rotor 42 and the circumferential wall 46 a. The coolant flowing into the gap between the rotor 42 and the circumferential wall 46 a flows in the rotation direction R through the gap between the rotor 42 and the circumferential wall 46 a with rotation of the rotor 42. In the portions where the pressurizing concave portions 500 and 502 are formed, the gaps between the rotor 42 and the circumferential wall 46 a are larger than those of the other portions. That is, the passage area of the coolant flowing through the gap between the rotor 42 and the circumferential wall 46 a is larger than that of the other portion where the pressurizing concave portions 500 and 502 are formed. As a result, when the coolant flows into the portion where the pressurizing concave portions 500 and 502 are formed, the coolant pressure becomes higher than the pressure in the other portions of the gap between the rotor 42 and the circumferential wall 46 a.

According to this configuration, due to the coolant flowing through the gap between the rotor 42 and the circumferential wall 46 a, force directed from the low pressure region LP to the high pressure region HP is applied to the end portion of the rotor 42 closer to the impeller 26. On the other hand, due to the coolant flowing through the gap between the rotor 42 and the circumferential wall 46 a, force directed from the high pressure region HP to the low pressure region LP is applied to the end portion of the rotor 42 opposite to the impeller 26. According to this configuration, it is possible to suppress displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. As a result, the contacting between the rotating body 60 and the casing 12 is suppressed, and a decrease in the pumping efficiency of the electric pump 10 is suppressed.

In a modification, any one of the pressurizing concave portions 500 and 502 may be formed. Moreover, the shape of the pressurizing concave portions 500 and 502 is not limited to the shape of the present embodiment. For example, the pressurizing concave portion 500 may be formed so that the circumferential wall 46 a is gradually separated from the outer circumferential surface 42 a. In general, the pressurizing concave portions 500 and 502 may be formed so that the circumferential wall 46 a is separated from the outer circumferential surface 42 a.

Seventh Embodiment

Differences from the electric pump 10 of the first embodiment will be described with reference to FIG. 10. In the electric pump 10 of the present embodiment, the facing wall 46 b has a different shape from that of the first electric pump 10. A pressurizing concave portion 600 is formed in a portion of the facing wall 46 b closer to the low pressure region LP. The pressurizing concave portion 600 extends in the rotation direction R on the low pressure region LP in a circular are shape. A portion of the facing wall 46 b where the pressurizing concave portion 600 is formed is further separated from the end surface 42 b than the other portion of the facing wall 46 b. Thus, the gap between the end surface 42 b and the facing wall 46 b on the low pressure region LP is larger than the gap between the end surface 42 b and the facing wall 46 b on the high pressure region HP.

During the operation of the electric pump 10, a portion of the coolant in the coolant passage 24 flows into the gap between the end surface 42 b and the facing wall 46 b. The coolant flowing into the gap between the end surface 42 b and the facing wall 46 b flows in the rotation direction R through the gap between the end surface 42 b and the facing wall 46 b with rotation of the rotor 42. In the portion where the pressurizing concave portion 600 is formed, the gap between the end surface 42 b and the facing wall 46 b is larger than that of the other portion. Thus, the passage area of the coolant flowing through the gap between the end surface 42 b and the facing wall 46 b is larger than that of the other portion where the pressurizing concave portion 600 is formed. As a result, when the coolant flows into the portion where the pressurizing concave portion 600 is formed, the coolant pressure becomes higher than the pressure in the other portion of the gap between the end surface 42 b and the facing wall 46 b.

According to this configuration, due to by the coolant flowing through the portion where the pressurizing concave portion 600 is formed, force directed toward the impeller 26 is applied to the end surface 42 b of the rotor 42. According to this configuration, it is possible to suppress displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. As a result, the contacting between the rotating body 60 and the casing 12 is suppressed, and a decrease in the pumping efficiency of the electric pump 10 is suppressed.

The shape of the pressurizing concave portion 600 is not limited to the shape of the present embodiment. For example, the pressurizing concave portion 600 may be formed so that the facing wall 46 b is gradually separated from the end surface 42 b. In general, the pressurizing concave portion 600 may be formed so that the facing wall 46 b is separated from the end surface 42 b.

Eighth Embodiment

Differences from the electric pump 10 of the first embodiment will be described with reference to FIG. 11. The rotating body 60 is not illustrated in FIG. 11 for the sake of description. In the electric pump 10 of the present embodiment, two pressurizing grooves 700 are formed on the circumferential wall 46 a. Each pressurizing groove 700 extends in a curved form from a position that faces an end portion of the rotor 42 closer to the impeller 26 on the low pressme region LP and reaches a position that faces an end portion of the rotor 42 opposite to the impeller 26 on the high pressure region HP. The two pressurizing grooves 700 are formed symmetrical about the XZ-plane that passes through the rotary shaft

In this configuration, the coolant flowing through the gap between the rotor 42 and the facing wall 46 a is pressurized by the pressurizing groove 700. Moreover, the pressurized coolant passes through the pressurizing groove 700 and reaches the end portion of the rotor 42 opposite to the impeller 26 on the high pressure region HP. Further, the pressurized coolant passes through the pressurizing groove 700 and reaches the end portion of the rotor 42 closer to the impeller 26 on the low pressure region LP. According to this configuration, the force of pressure difference between the coolant flowing through the portion where the pressurizing groove 700 is formed and the coolant flowing though the other portion is applied to the rotor 42. According to this configuration, it is possible to suppress the displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. As a result, the contacting between the rotating body 60 and the casing 12 is suppressed, and a decrease in the pumping efficiency of the electric pump 10 is suppressed.

Ninth Embodiment

Differences from the electric pump 10 of the first embodiment will be described with reference to FIG. 12. In the electric pump 10 of the present embodiment, a permanent magnet 804 that surrounds the impeller 26 is attached to the outer circumferential surface of the impeller 26. The outer surface of the permanent magnet 804 is an N-pole. Two permanent magnets 800 and 802 are disposed inside the upper casing 28. The permanent magnet 800 is provided on the high pressure region HP. The permanent magnet 800 faces the outer surface of the permanent magnet 804, and the facing surface is an S-pole. The permanent magnet 802 is provided on the low pressure region LP. The permanent magnet 802 faces the outer surface of the permanent magnet 804, and the facing surface is an N-pole. The magnetic polarities of the permanent magnets are not limited to the above configuration, and the polarities of the permanent magnets 800 to 804 may be reversed.

Due to the permanent magnets 800 and 804, magnetic force directed from the low pressure region LP to the high pressure region HP is applied to the impeller 26. Similarly, due to the permanent magnets 802 and 804, magnetic force directed from the low pressure region LP to the high pressure region HP is applied to the impeller 26. That is, during the operation of the electric pump 10, due to the permanent magnets 800 to 804, magnetic force directed from the low pressure region LP to the high pressure region HP is constantly applied to the impeller 26. According to this configuration, it is possible to further suppress the displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. As a result, the contacting between the rotating body 60 and the casing 12 is suppressed, and a decrease in the pumping efficiency of the electric pump 10 is suppressed.

In a modification, any one of the two permanent magnets 800 and 802 may be comprised. Moreover, when only the permanent magnet 800 is comprised, the impeller 26 may comprise a magnetic body (for example, a metallic component or the like) that surrounds the outer circumference of the impeller 26 instead of the permanent magnet 804. In this configuration, due to the permanent magnet 800 and the magnetic body, magnetic force directed from the low pressure region LP to the high pressure region HP is applied to the impeller 26.

Alternatively, a magnetic body may be disposed instead of the permanent magnet 800. In this configuration, due to the permanent magnet 804 and the magnetic body, magnetic force directed from the low pressure region LP to the high pressure region HP is applied to the impeller 26.

Tenth Embodiment

Differences from the electric pump 10 of the first embodiment will be described with reference to FIG. 13. In the electric pump 10 of the present embodiment, the rotor 42 comprises a permanent magnet 904 that is disposed on the end surface 42 b so as to surround the shaft 16. The lower surface of the permanent magnet 904 is an N-pole. Two permanent magnets 900 and 902 are disposed on the facing wall 46 b. The permanent magnet 900 is provided on the high pressure region HP. The permanent magnet 900 faces the lower surface of the permanent magnet 904, and the facing surface is an S-pole. The permanent magnet 902 is provided on the low pressure region LP. The permanent magnet 902 faces the lower surface of the permanent magnet 904, and the facing surface is an N-pole.

According to this configuration, similarly to the ninth embodiment, due to the magnetic force of the permanent magnets 900 to 904, it is possible to suppress the displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. As a result, the contacting between the rotating body 60 and the casing 12 is suppressed, and a decrease in the pumping efficiency of the electric pump 10 is suppressed.

In a modification, only one of the two permanent magnets 900 and 902 may be comprised. Moreover, when only the permanent magnet 900 is comprised, the rotor 42 may comprise a magnetic body that surrounds the outer circumference of the impeller 26 instead of the permanent magnet 904. In this configuration, due to the permanent magnet 900 and the magnetic body, magnetic force directed from the low pressure region LP to the high pressure region HP is applied to the impeller 26.

Alternatively, a magnetic body may be disposed instead of the permanent magnet 900. In this configuration, due to the permanent magnet 904 and the magnetic body, magnetic force directed from the low pressure region LP to the high pressure region HP is applied to the impeller 26.

Eleventh Embodiment

Differences from the electric pump 10 of the first embodiment will be described with reference to FIG. 14. In the electric pump 10 of the present embodiment, a permanent magnet 1004 that surrounds the impeller 26 is attached to an outer edge of a surface of the impeller 26 closer to the rotor 42. The surface of the permanent magnet 1004 closer to the rotor 42 is an N-pole. A permanent magnet 1002 is disposed in the lower casing 46. The permanent magnet 1002 is provided on the low pressure region LP. The permanent magnet 1002 faces the surface of the permanent magnet 1004 closer to the rotor 42, and the facing surface is an N-pole. The magnetic poles of the permanent magnets are not limited to the above configuration, and the polarities of the permanent magnets 1002 and 1004 may be reversed.

On the low pressure region LP, due to the permanent magnets 1002 and 1004, magnetic force is applied to the surface of the impeller 26 closer to the rotor 42 in such a direction that the surface is pressed upward. According to this configuration, it is possible to further suppress the displacement of the rotating body 60 resulting from the coolant pressure difference in the coolant passage 24. As a result, the contacting between the rotating body 60 and the casing 12 is suppressed, and a decrease in the pumping efficiency of the electric pump 10 is suppressed.

In a modification, the lower casing 46 may comprise a permanent magnet that is provided on the high pressure region HP and faces the permanent magnet 1004. In this case, the facing surface of the permanent magnet facing the permanent magnet 1004 may have a magnetic polarity opposite to that of the surface of the permanent magnet 1004 closer to the rotor 42. In this case, the impeller 26 may comprise a magnetic body (for example, a metallic component or the like) that surrounds the outer circumference of the impeller 26 instead of the permanent magnet 1004. Alternatively, a magnetic body may be disposed on the high pressure region HP of the lower casing 46 instead of the permanent magnet.

Modifications

(1) The electric pump 10 may include two or more of the plurality of configurations disclosed in the first to tenth embodiments. For example, the electric pump 10 may comprise the configuration (that is, the configuration of the two cores 144 a and 144 b) disclosed in the second embodiment, the configuration (that is, the first and second core plates 248 a and 2486) of the third embodiment, and the configuration (that is, the pressurizing concave portions 500 and 502) of the sixth embodiment.

(2) The technique disclosed in the present application is also useful in an electric pump in which the cores 44 a and 44 b of the stator 44 are integrated. For example, as shown in FIG. 15, the stator may comprise one core 1144. The core 1144 may comprise first three teeth 1170 a and second three teeth 1170 b. The first three teeth 1170 a may be disposed on the low pressure region LP. The tip ends of the three teeth 1170 a may face the outer circumferential surface 42 a of the rotor 42. A portion of each of the first teeth 1170 a facing the end portion of the rotor 42 closer to the impeller 26 may be further separated from the outer circumferential surface 42 a of the rotor 42 than portions facing the other portions of the rotor 42. The second three teeth 11706 may be disposed on the high pressure region HP. The tip ends of the three teeth 1170 b may face the outer circumferential surface 42 a of the rotor 42. A portion of each of the second teeth 1170 b facing the end portion of the rotor 42 opposite to the impeller 26 may be further separated from the outer circumferential surface 42 a of the rotor 42 than portions facing the other portions of the rotor 42. According to this configuration, the same advantages as the fifth embodiment can be obtained.

(3) In the embodiments described above, the core 44 a or the like is formed by stacking a plurality of core plates 48 or the like. However, the core 44 a or the like may be configured as an integral body.

(4) In the sixth to eleventh embodiments described above, although the electric pump 10 comprises the same stator 44 as the first embodiment, the electric pump 10 may comprise a stator 44 that comprises two cores that are provided bilaterally symmetrically about the rotor 42.

(5) The technique disclosed in the present application can be used in an electric pump for fluid (for example, liquid fuel, warm water, or the like) other than a coolant. 

What is claimed is:
 1. An electric pump comprising: a rotating body comprising a rotor and an impeller disposed juxtaposed to the rotor in a rotary shaft direction of the rotor; a stator disposed on an outer circumferential side of the rotor; a casing comprising a fluid passage formed along an outer circumference of the impeller, and configured to store the rotating body and the stator; and a loading unit configured to constantly apply force on the rotating body during when the electric pump is operating, wherein the force being for reducing displacement of the rotating body caused by a pressure difference in the fluid passage generated when the electric pump is operating between a low pressure side where a pressure of fluid is low and a high pressure side where the pressure of the fluid is high within the fluid passage.
 2. The electric pump as in claim 1, wherein the loading unit comprises a first configuration, a second configuration, or both of the first and second configurations, the first configuration is a configuration in which resultant force of magnetic force loaded on an end portion of the rotor on an impeller side is directed from the low pressure side to the high pressure side, and the second configuration is a configuration in which resultant force of magnetic force loaded on an end portion of the rotor on an opposite side from the impeller is directed from the high pressure side to the low pressure side.
 3. The electric pump as in claim 2, wherein the loading unit includes a stator and a rotor, the first configuration includes a configuration in which an area of the stator extending along the end portion of the rotor on the impeller side on the high pressure side is larger than an area of the stator extending along the end portion of the rotor on the impeller side on the low pressure side, and the second configuration includes a configuration in which an area of the stator extending along the end portion of the rotor on the opposite side from the impeller on the low pressure side is larger than an area of the stator extending along the end portion of the rotor on the opposite side from the impeller on the high pressure side.
 4. The electric pump as in claim 3, wherein the first configuration includes a configuration in which an end portion of a high pressure-side stator portion positioned on the high pressure side of the stator extends toward the impeller side along the rotary shaft direction than an end portion of a low pressure-side stator portion positioned on the low pressure side of the stator, and the second configuration includes a configuration in which an end portion of the low pressure-side stator portion on the opposite side from the impeller extends toward the opposite side from the impeller along the rotary shaft direction than an end portion of the high pressure-side stator portion on the opposite side from the impeller.
 5. The electric pump as in claim 3, wherein the first configuration includes a configuration in which a length of a high pressure-side stator portion extending along an outer circumferential surface of the rotor is longer than a length of a low pressure-side stator portion extending along the outer circumferential surface of the rotor in a cross section vertically intersecting a rotary shaft at the end portion of the rotor on the impeller side, and the second configuration includes a configuration in which a length of the low pressure-side stator portion extending along the outer circumferential surface of the rotor is longer than a length of the high pressure-side stator portion extending along the outer circumferential surface of the rotor in a cross section vertically intersecting the rotary shaft at the end portion of the rotor on the opposite side from the impeller.
 6. The electric pump as in claim 2, wherein the load unit includes a stator and a rotor, the first configuration includes a configuration in which an average gap size between the rotor and a high pressure-side stator portion positioned on the high pressure side of the stator is smaller than an average gap size between the rotor and a low pressure-side stator portion positioned on the low pressure side of the stator at the end portion of the rotor on the impeller side, and the second configuration includes a configuration in which an average gap size between the rotor and the low pressure-side stator portion is smaller than an average gap size between the rotor and the high pressure-side stator portion at the end portion of the rotor on the opposite side from the impeller.
 7. The electric pump as in claim 1, wherein the loading unit includes a first magnetic body attached to the rotating body and circumscribing in a circumferential direction of the rotating body, and a second magnetic body attached to a region of the casing that faces the first magnetic body, the second magnetic body comprises a first magnetic sub-body, a second magnetic sub-body, or both the first and second magnetic sub-bodies, the first magnetic sub-body is disposed on the high pressure side, and generates magnetic force in a direction that draws the first magnetic body toward the second magnetic body, and the second magnetic sub-body is disposed on the low pressure side, and generates magnetic force in a direction that presses the first magnetic body toward an opposite side from the second magnetic body.
 8. The electric pump as in claim 7, wherein the first magnetic body is attached to the impeller
 9. The electric pump as in claim 7, wherein the first magnetic body is attached to an end surface of the rotor on the opposite side from the impeller.
 10. The electric pump as in claim 1, wherein the loading unit includes a circumferential wall that covers the stator and surrounds a circumference of the rotor, the fluid passage communicates with a gap between the circumferential wall and the rotor, the loading unit includes a third configuration, a fourth configuration, or both the third and fourth configurations, the third configuration is a configuration in which a gap between the circumferential wall and the rotor on the low pressure side is larger than a gap between the circumferential wall and the rotor on the high pressure side at the end portion of the rotor on the impeller side, and the fourth configuration is a configuration in which a gap between the circumferential wall and the rotor on the high pressure side is larger than a gap between the circumferential wall and the rotor on the low pressure side at the end portion of the rotor on the opposite side from the impeller.
 11. The electric pump as in claim 1, wherein the loading unit includes a facing wall that faces an end surface of the rotor on the opposite side from the impeller, the fluid passage communicates with a gap between the facing wall and the rotor, and the loading unit includes a configuration in which a gap between the facing wall and an end surface of the rotor on the opposite side from the impeller that is on the low pressure side is larger than a gap between the facing wall and an end surface of the rotor on the opposite side from the impeller that is on the high pressure side. 